A&P Unit 3 Lab: Chapter 19
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Neurons, the Spinal Cord, and Spinal Nerves
151 Terms
What two organs make up the central nervous system (CNS)?
The brain and spinal cord
What is the CNS above the foramen magnum considered?
The brain
What is the CNS below the foramen magnum considered?
The spinal cord
What are the three general functions of the spinal cord?
Carry sensory information upward, carry motor commands downward, and process information/execute reflexes
How many pairs of spinal nerves are there?
31 pairs
Are spinal nerves sensory, motor, or both?
Both (mixed nerves)
What do spinal nerves carry?
Sensory and motor information to and from the spinal cord
What are the three major functional classes of neurons?
Sensory neurons, interneurons, and motor neurons
What do sensory neurons do?
Carry signals from sensory receptors to the CNS
What type of neuron are most sensory neurons?
Unipolar neurons
What do interneurons do?
Send signals to other neurons within the CNS
What do motor neurons do?
Send signals from the CNS to effectors
What are the body's effectors?
Glands and muscle cells
What do visceral motor neurons control?
Glands, cardiac muscle, and smooth muscle
What neurons control skeletal muscle?
Somatic motor neurons
What is the general function of a neuron?
To respond to a stimulus by generating an electrical impulse that signals another cell
What are the three main structural features of a neuron?
Dendrites, cell body (soma), and axon
What is the function of dendrites?
They receive stimuli/signals
What is another name for the neuron's cell body?
Soma
What is the function of the axon?
It sends electrical impulses to another cell or cells
What type of neuron is a somatic motor neuron?
A multipolar neuron
What does multipolar mean?
The neuron has numerous dendrites and a single axon
Where are the cell bodies and dendrites of somatic motor neurons located?
In the CNS
Where does the axon of a somatic motor neuron extend?
Into the periphery
What cells do somatic motor neurons send signals to?
Skeletal muscle cells
What is this an image of?
Neuron
What is the purple arrow pointing at?
Nissl body
What is the blue arrow pointing at?
Nucleus
What part of the neuron is being outlined in blue?
Soma (neuron body)
What are the red arrows pointing at?
Dendrites
What structures are the blue arrows pointing at?
Telodendria
What structures are the purple arrows pointing at?
Axon terminals
What is being outlined in blue?
Axon hillock
What are the blue arrows pointing at?
Axolemma
What is being outlined in purple?
Neurolemmocytes (Schwann cells)
What is the blue arrow indicating?
Node of Ranvier
What is the blue arrow indicating?
Neurilemma
What is the blue arrow indicating?
Endoneurium
Is this a unipolar or multipolar neuron?
Multipolar
What type of neurons are being shown in this image?
Motor neurons
What is the blue arrow pointing at?
Soma
What is the blue arrow pointing at?
Dendrite
What is the blue arrow pointing at?
Nucleus of a glial cell
Are these unipolar or multipolar neurons?
Unipolar
What type of neuron is this?
Sensory
What is being circled in red?
Soma
What is the red arrow pointing at?
Glial cell
What structures can extend from the soma of a somatic motor neuron?
One axon and multiple dendrites
What is the soma?
The cell body of the neuron
What is found inside the soma?
The nucleus
What is the dark spot inside the nucleus called?
The nucleolus
What is the plasma membrane of the axon called?
The axolemma
What cells wrap around the axon to form the myelin sheath?
Neurolemmocytes (Schwann cells)
What are the gaps between neurolemmocytes called?
Nodes of Ranvier
What surrounds the axon and its myelin sheath?
The endoneurium
What are telodendria?
Branches at the end of an axon
What are synaptic knobs?
The endings of axon branches that form synapses with other cells
What do telodendria do?
Form synapses with other cells
Where do telodendria and synaptic knobs from other neurons form synapses on a somatic motor neuron?
On the dendrites and soma
What is the axon hillock?
The cone-shaped part where the axon starts at the soma
What is the proper name for the “nodes of Ranvier”
Neurofibril nodes
Where does the spinal cord begin?
At the foramen magnum
At the foramen magnum
Near the L1 vertebra
Where does the the spinal cord occupy?
Vertebral cavity
What forms the vertebral cavity?
The vertebral foramina of the vertebrae.
What is the inferior tip of the spinal cord called?
Conus medullaris
What is the name of the collection of spinal nerves below the conus medullaris?
Cauda equina
What is the function of the filum terminale?
It attaches the conus medullaris to the coccyx
What are the two enlargements of the spinal cord?
Cervical enlargement and lumbosacral enlargement
What is the cervical enlargement associated with?
Nerves that supply the upper limbs
What is the lumbosacral enlargement associated with?
Nerves that supply the lower limbs
What groove runs down the back of the spinal cord?
Posterior median sulcus
What groove runs down the front of the spinal cord?
Anterior median fissure
What are plexuses?
Networks formed when the anterior rami of spinal nerves intermingle
Which spinal nerves form the cervical plexus?
C1–C4
What does “innervate” mean?
To supply a body part with nerves so it can receive or send signals
What does the cervical plexus innervate?
Muscles and skin of the neck, parts of the head, and shoulders
What important nerve comes from the cervical plexus?
Phrenic nerve
What does the phrenic nerve control?
The diaphragm, making it important for breathing
Which spinal nerves form the brachial plexus?
C5–T1
What does the brachial plexus innervate?
The pectoral girdles and upper limbs
Which spinal nerves form the lumbosacral plexus?
L1-S4
What does the lumbosacral plexus supply?
The lower limbs
What is the largest nerve in the body?
The sciatic nerve
What do the sciatic nerves innervate?
Much of the lower limbs
What is sciatica?
Pain or numbness caused by irritation or injury to spinal nerves contributing to the sciatic nerve
What are the anterior rami of most thoracic spinal nerves called?
Intercostal nerves
Where do intercostal nerves travel?
Between the ribs
What are the three spinal meninges?
Pia mater, arachnoid mater, and dura mater
What is found in the subarachnoid space?
Cerebrospinal fluid (CSF)
How many layers does the spinal dura mater have?
One layer
What is the epidural space?
A space between the spinal dura mater and the vertebrae
What is found in the epidural space?
Adipose tissue and blood vessels
Is there an epidural space around the cranial meninges?
No
What is the blue arrow pointing at?
Anterior median fissure
What region of the spinal cord is this?
Cervical spinal cord
What part of the spinal cord is this?
Cervical enlargement
What part of the spinal cord is this?
Cervical plexus
What is this?
Phrenic nerve
What part of the spinal cord is this?
Brachial plexus